This invention relates to magnetic head assemblies for producing a vertically magnetized record and more particularly to magnetic head assemblies for producing a vertically magnetized record which is also capable of reading or reproducing vertically magnetized recorded information.
A magnetic recording method has been previously known in which information is written onto and read off a magnetic recording medium having a magnetic layer with a ring-type magnetic head having a nonmagnetic gap. The magnetic layer may have been formed by dispersing in a binder a magnetic powder of .gamma.-Fe.sub.2 O.sub.3, .gamma.-Fe.sub.2 O.sub.3 doped with Co, Fe.sub.3 O.sub.4 doped with Co, a berthollide compound of .gamma.-Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, CrO.sub.2 or ferromagnetic metallic alloy. This magnetic recording method is extensively employed to record and reproduce audio signals, video signals, measurement signals, and digital signals used in computers. Furthermore, since the quantity of information to be recorded is increasing day-by-day, a method of recording signals of short wavelength in a magnetic recording medium has been in strong demand so that the recording density may be increased.
However, it should be noted that the conventional magnetic recording method is a so-called "butt magnetization system" in which a ring-type magnetic head is used to magnetize the magnetic layer lengthwise along a track in parallel with the longitudinal direction of the magnetic recording medium to record information. Because of this, if the wavelength of data to be recorded is short, the self-demagnetization loss is increased, and accordingly, a sufficient output can not be obtained.
In addition, this magnetic recording system has a recording demagnetization action which results in difficulties in recording signals of short wavelengths. That is, when the magnetic recording medium moves relative to the ring-type magnetic recording head, the recording point in the magnetic recording medium is subjected to polarity inversion by a magnetic field signal created by the recording head so that a rotational magnetization mode occurs in the magnetic recording layer. As the rotational magnetic mode has a closed magnetic path, the leakage magnetic field outside the magnetic recording medium is greatly decreased and no lines of magnetic force are available to be picked up by the reproducing head so that no data is apparently recorded. Accordingly, it is not possible to reproduce any output.
This phenomenon becomes significant when the wavelength of data to be recorded is short. The output of reproduction can be increased to an extent by increasing the recording current, however, this quickly reaches a maximum value. If the recording current were to be still further increased, a "dip" phenomenon occurs in which the reproduced output decreases then reaches a second maximum value. Thus, it is fundamentally impossible to solve the problem by increasing the recording current. The phenomenon occurs in magnetic recording methods using either a bias system or a biasless system. In either case, it is quite difficult to increase the magnetic record density.
A magnetic recording system which overcomes these problems and makes it possible to record data of short wavelengths has been disclosed. Such a system is a vertical magnetization system in which the magnetic recording layer is magnetized perpendicularly to the surface of the surface of the magnetic recording medium in order to record information.
In this recording system, a main head for vertical magnetization is provided on the magnetic recording layer side of a magnetic recording medium of which a magnetic recording layer is formed on a supporting substrate and an auxiliary head is provided on the opposite side of the same. The auxiliary head is provided with a winding. A current modulated in accordance with information to be recorded is supplied to this winding to create a magnetic field which magnetizes the main head. A vertical magnetic field created simultaneously magnetizes the recording medium to produce the vertical magnetization recording. Signals recorded according to this vertical magnetization recording system may be reproduced or played back using the same head as used for recording. However, if the film thickness (corresponding to the gap of the ring-type head) of the main head is reduced, the reproduction sensitivity is lowered considerably for reproducing signals of short wavelengths. Thus, the method is not entirely suitable for the reproduction of signals of short wavelengths which is a supposed advantage of the prior art vertical magnetization recording system.
A reproduction method using a conventional ring-type head for signals recorded using the vertical magnetization recording system has been proposed. However, this method suffers from problems in implementation in that reproduction of signals of short wavelengths cannot be adequately carried out because of a so-called "gap loss". Also, track positioning and azimuth adjustments with respect to the vertical magnetization recording head are necessitated.